1. Field of the Invention
This invention relates to medical instruments and in particular to a trocar that houses a pneumo-needle for making the pilot entry wound.
2. Description of Related Art
Trocars are sharp pointed surgical instruments used to puncture a body cavity. This is frequently done so that fluids can be drained using a cannula inserted into the opening. Trocars are also used during endoscopic and laparoscopic diagnostic and therapeutic procedures. A conventional endoscopic procedure follows three steps. The first step is the insertion of a Veress cannula into the abdominal cavity through a small incision in the abdominal wall. The Veress cannula includes a hollow pneumo or Veress needle having a sharp point. When the cavity is entered, a spring-loaded obturator inside the lumen of the needle pops out to extend a short distance beyond the needle's sharp point. This protects against an inadvertent laceration of intra-abdominal structures. Because the obturator is spring-loaded, it is not able to protrude beyond the needle's point until the abdominal cavity is entered. Next, the abdominal cavity is inflated with a gas through a small lumen in the obturator of the Veress cannula. After inflation, the Veress cannula is removed. Finally, a standard trocar housed within the lumen of a trocar tube is thrust into the inflated abdomen to increase the size of the opening. Standard trocars are shaped like a large metal peg with a sharpened point, having a diameter varying from 3-12 mm. The trocar is then removed and an endoscopic instrument is inserted into the abdominal cavity through the trocar tube.
A major problem with standard trocars is that the sharpened tip of the trocar, after being thrust through the abdominal wall, can inadvertently puncture or lacerate intra-abdominal tissue. Also, standard conventional trocars are generally not disposable and after reuse, the tips become dull, requiring frequent sharpening, otherwise the force to enter the abdomen gets unacceptably high.
U.S. Pat. No. 4,601,710 and U.S. Pat. No. 4,535,773 describe embodiments of a disposable trocar which include a spring-bodied tubular protective shield. One embodiment describes a trocar whose piercing tip is formed of three blades. The shield of this trocar is a tubular body having a frustoconical end that is slotted to receive the blades. In a second embodiment, which was considered to be an improvement over the first, the piercing tip is pyramidal and is formed by three bevels in the end of an otherwise cylindrical body. The second embodiment also has a shield locking mechanism. Both embodiments also have sealing valves within the cannula tube, to prevent gas leaking from the abdominal cavity during operative procedures. While these embodiments are an improvement over standard trocars, the cutting action and force required to thrust the trocar into the abdomen is still large due to the configuration of the cutting tip and the force required to compress the shield. This creates a plunging effect which results in a high probability of inadvertently striking and damaging abdominal tissues.
In addition to the above, current valve designs within the cannula tube do not optimally restrict gas leakage, and because of their configuration and action, they interfere with endoscopic instruments which pass through into the abdominal cavity. Further, the initial step of inserting the Veress cannula creates an additional hole. There is, therefore, a significant need: to improve the performance of the piercing tip to reduce the force of insertion of the trocar; to eliminate one step of the current procedure; to add levels of safety by controlling the depth of penetration of thrust, eliminating the plunging effect; and to improve the cannula seal to minimize gas leakage and reduce interference with endoscopic instruments passing through into the abdominal cavity.
A combined laparoscopic trocar and pneumo-needle is described in Soviet Patent SU 1445-713-A issued Dec. 23, 1988. That laparoscope trocar includes a pneumoperitoneum needle with an introduction depth limiter and an underspring mandrel having a blunt working end. A socket on the working end includes a side aperture and a longitudinal groove in its inner surface which joins with the side aperture at a connection. In other words, the pneumo-needle is housed in a channel in the trocar. The Soviet device also includes an obturator safety tip and a depth control mechanism.
Other patents describe combined pneumo-needles and trocars. See, for example, U.S. Pat. No. 4,535,773 which discloses a trocar having a needle which passes through the side of the tip. Other patents describe needles or guidewires which emerge from near the tip of a trocar-like puncture peg. Note specifically: U.S. Pat. No. 4,808,157; U.S. Pat. No. 5,135,525; and, U.S. Pat. No. 3,459,189.
Attempts have been made in the prior art to avoid making more puncture holes in the patient than are absolutely necessary. This concept is suggested, for example, in U.S. Pat. No. 4,986,814 entitled ONE-PUNCH CATHETER.
U.S. Pat. No. 4,994,042 entitled COMBINED CATHETER AND NEEDLE is of possible relevance in that it describes the combination of diverse puncture mechanisms.
U.S. Pat. No. 4,686,984 entitled CATHETER FOR WIDENING A PUNCTURE HOLE describes a device for widening puncture channels through the use of progressively bigger enlarging elements.
The following patents are cited with regard to their general teaching in the area of combined pneumo-needle and trocar devices: 4,249,541; 5,059,183 and 5,066,288.
The use of graduated scales in the context of a specific puncture mechanism is described in U.S. Pat. No. 4,760,847 and is discussed, to a limited extent, in Soviet Patent SU 1445-713-A, previously described.
There appears to be very little relevant art with regard to the use of stamped tips for trocar-like instruments. Of possible relevance, however, might be U.S. Pat. No. 5,057,082 entitled TROCAR ASSEMBLY which generally discusses the structure of a particular trocar tip but otherwise does not appear to be relevant to the concept of using stamped materials therefore.
The prior art taken as a whole does not appear to teach or suggest combining a pneumo-needle, trocar and sleeve into a single apparatus having the benefits of the present invention. Among the many benefits of the present invention are the elimination of the plunging effect by limiting penetration into the body cavity and the simultaneous reduction of force necessary to pierce the abdominal wall through the use of an eccentric located pilot needle. The one cycle locking feature of the obturator adds significant safety to the surgical procedure. Several other features of the invention are significant improvements over the prior art. The advantages of the combined eccentrically housed pneumo-needle/trocar invention are the following: a reduction in the number of steps with respect to prior art procedures; one fewer hole required to be made in the abdominal cavity; a piloted piercing tip with lower force required to thrust the trocar through the abdominal wall; a pneumo-needle obturator locking mechanism which provides visual, audible and tactile feedback to indicate when the abdominal cavity has been penetrated; a color-coded graduated pneumo-needle, which is setable in order to measure depth, coinciding with the patient's abdominal wall thickness, to which the pneumo-needle is to be penetrated into the abdominal cavity, thereby eliminating unnecessary plunging and the resultant possible tissue damage; a sealing means within the trocar tube which offers less interference than prior art devices to endoscopic instruments as they are manipulated during operative procedures and wherein the seals offer greater restriction with respect to gas leakage during procedures as the endoscopic instruments are passed through the device or after the trocar has been withdrawn; providing the availability of additional 1.5 mm and 3.0 mm access lumens within the same instrument; and, in general, a more suitably ergonometrically configured device.